Question

A pulse (shown here) is first reflected from the free end $A$ and then from the rigid end $B$. The phase difference between initial incident pulse and final reflected pulse after two reflections is

• A. $\pi$
• B. $2\pi$
• C. $0$
• D. $3\pi$

Answer 1

The correct option is A $\pi$

$1^{\text{st}}$ reflection :
The end $A$ is free, therefore, pulse gets reflected without any inversion. So, phase change is zero.

$2^{\text{nd}}$ reflection :
The end $B$ is fixed, therefore, reflected pulse has phase difference of $\pi$.

$\therefore$ After two reflections, resultant phase difference is $\pi$ between initial and final pulses.